[Influence of different disturbance intensity on the phosphorus adsorption and immobilization by the sediments from an inner city heavily polluted canal].

The mechanism of phosphorus (P) adsorption and immobilization under different disturbance intensities was investigated in laboratory. The sediments and water used were taken from an inner-city heavily polluted canal. Addition of KH2PO4 into the experimental units were made similar to the external P input into the canal and carried out periodically. The results show that sediment disturbance could increase the P adsorption amount by suspended solids. The higher disturbance intensity is, the greater P adsorption amount is obtained. Dissolved inorganic P (DIP) is the main form of additional KH2PO4, but sediment disturbance enhances the transformation of P from DIP to PP (particulate P), indicating that sediment disturbance decreases the bioavailable P in the overlying water. Sequential fractionation indicated that the NH4Cl-P decreased, but the Fe/Al-P, HCl-P and Res-P increased. More than 80% (the average value under three disturbance intensities) of the incorporated P accounts for Fe/Al-P in the sediments. The incorporated Fe/Al-P accounts for 37.49% (100 r x min(-1)), 42.32% (200 r x min(-1)) and 54.24% (300 r x min(-1)) of non-occluded Fe/Al-P in the sediments respectively, indicating that the percentage of incorporated P to occluded Fe/Al-P decreases with the increase of disturbance intensity. The variation of HCl-P under the same disturbance intensity is the same as the occluded Fe/Al-P. It suggests that the continuous addition of external P is mainly incorporated into the mobile P forms under short-term and high-intensity disturbance, which means the adsorption of P by sediments is the short-term immobility.